Description:
VU (Voltage Unit) meters are often included in analog audio equipments to display a signal level in Visual Units. We are building a mono input VU meter in this project. You can build one pair to use them in stereo mode.
Structure: Input sensitivity is about 1 Volt rms, up to +6dB. You can adjust the input amplitude by using the multiturn 50k linear potentiometer (POT1). Circuit needs symmetric ±12V power supply because of the LM324 opamp. We used metal film resistors (1% Tolerance) so accuracy is sufficiently high. Visual duration can be adjusted by using linear 10k potentiometer (POT2). LEDs should be 5mm x 5mm in size for best fit. But we used standard LEDs and this caused a little shift as you can see from the image. Dot/Bar switch determines the operation mode of LM3915.
PCB is 1:1 scaled. You can print and transfer without making any change.
